Truck Minor Vibration over 70 MPH?

Sometimes when going down a hill at 70 MPH or higher, I sense this minor vibration. I’m in the process of changing my leveling valve rod/link, but are there other components that could be causing this? The leveling valve itself? I don’t think it has ever been changed. This is on a 2014 Freightliner Cascadia DD15 with 745k miles.

It vibrates for one second, then it stops, and the cycle continues. Sometimes there is no vibration. I’m thinking the road itself may have something to do with it as well (asphalt vs concrete).

 

You say the vibration is when coming down hill, have you thought it may be linked to your Jakes somehow.

 

For this vibration, my jakes were not turned on.

 

Possible slop in the drivelines, maybe slip yokes.

 

Not sure how one associates a vibration with a leveling valve. Care to elaborate on the thought process behind this?

 

I’m not sure either, but I’ve heard some mention it.

 

Suspension ride height is one of the most common areas of driveline vibration issues. If the ride height is high or low from spec the driveshafts and ujoint operating angles can be extreme and will cause a vibration that can come and go upon accell and decell. This type of vibration will usually be felt in your feet and it your seat, maybe the shifter as well.

The leveling valve is the valve the maintains the suspension ride height and is most often the adjustment point to set the desired ride height level. This is something that is easy to check and set and is always first on the list to check when troubleshooting a vibration complaint.

 

I'd start with the easy stuff first: tires(inflation, balance, out of round, flat spots) and then the shocks and then the alignment.

Good Luck!

 

Don’t forget wheels, check for bent rim, by spinning wheel against a stationary object. Aluminum’s can get distorted easier and quicker than you’d think. Especially steers.

 

I’m gonna guess it’s probably on or more of the wheel balances. Spin balancing being set on a machine, doesn’t mean it stays balanced at all speeds.I don’t know about Trucks, but high speed on the Car balancing with a machine is done when other techniques don’t work. never seen if done on a Truck only Cars.Centramatics or equal, maybe? Otherwise it may be one of the driveshafts, since only downhill. A loose u- joint or not enough angle ( set too low ) causing vibrations. Drive shafts aren’t balanced as good as they can be, from the factory.